[PATCHv2 4/9] introduce the function virCgroupMoveTask()

[Hu Tao <hutao@xxxxxxxxxxxxxx>]

From: Wen Congyang <wency@xxxxxxxxxxxxxx>

introduce a new API to move all tasks from a cgroup to another cgroup
---
 src/libvirt_private.syms |    1 +
 src/util/cgroup.c        |   54 ++++++++++++++++++++++++++++++++++++++++++++++
 src/util/cgroup.h        |    2 +
 3 files changed, 57 insertions(+), 0 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 7d570b5..eda0808 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -88,6 +88,7 @@ virCgroupKill;
 virCgroupKillPainfully;
 virCgroupKillRecursive;
 virCgroupMounted;
+virCgroupMoveTask;
 virCgroupPathOfController;
 virCgroupRemove;
 virCgroupSetBlkioDeviceWeight;
diff --git a/src/util/cgroup.c b/src/util/cgroup.c
index 66d98e3..84a21ce 100644
--- a/src/util/cgroup.c
+++ b/src/util/cgroup.c
@@ -791,6 +791,60 @@ int virCgroupAddTask(virCgroupPtr group, pid_t pid)
     return rc;
 }
 
+static int virCgrouAddTaskStr(virCgroupPtr group, const char *pidstr)
+{
+    unsigned long long value;
+
+    if (virStrToLong_ull(pidstr, NULL, 10, &value) < 0)
+        return -EINVAL;
+
+    return virCgroupAddTask(group, value);
+}
+
+/**
+ * virCgroupMoveTask:
+ *
+ * @src_group: The source cgroup where all tasks are removed from
+ * @dest_group: The destination where all tasks are added to
+ *
+ * Returns: 0 on success
+ */
+int virCgroupMoveTask(virCgroupPtr src_group, virCgroupPtr dest_group)
+{
+    int rc = 0;
+    int i;
+    char *content, *value, *next;
+
+    for (i = 0 ; i < VIR_CGROUP_CONTROLLER_LAST ; i++) {
+        /* Skip over controllers not mounted */
+        if (!src_group->controllers[i].mountPoint ||
+            !dest_group->controllers[i].mountPoint)
+            continue;
+
+        rc = virCgroupGetValueStr(src_group, i, "tasks", &content);
+        if (rc != 0)
+            goto cleanup;
+
+        value = content;
+        while((next = strchr(value, '\n')) != NULL) {
+            *next = '\0';
+            if ((rc = virCgrouAddTaskStr(dest_group, value) < 0))
+                goto cleanup;
+            value = next + 1;
+        }
+        if (*value != '\0') {
+            if ((rc = virCgrouAddTaskStr(dest_group, value) < 0))
+                goto cleanup;
+        }
+
+        VIR_FREE(content);
+    }
+
+    return 0;
+
+cleanup:
+    return rc;
+}
 
 /**
  * virCgroupForDriver:
diff --git a/src/util/cgroup.h b/src/util/cgroup.h
index 315ebd6..308ea47 100644
--- a/src/util/cgroup.h
+++ b/src/util/cgroup.h
@@ -58,6 +58,8 @@ int virCgroupPathOfController(virCgroupPtr group,
 
 int virCgroupAddTask(virCgroupPtr group, pid_t pid);
 
+int virCgroupMoveTask(virCgroupPtr src_group, virCgroupPtr dest_group);
+
 int virCgroupSetBlkioWeight(virCgroupPtr group, unsigned int weight);
 int virCgroupGetBlkioWeight(virCgroupPtr group, unsigned int *weight);
 
-- 
1.7.4.4

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